The present invention relates generally to reformable materials, and more specifically to mixtures, primarily solid/liquid mixtures, that can be formed into desired shapes and then re-used to form other desired shapes. The desired shapes may be end products, or may be templates or tools used to form end products or other templates or tools.
The prior art for making molds or tooling deals for the most part with fabricating, machining, layered deposition forming, molding or casting of tools for a single dedicated purpose. While the tools may be modified or the materials recycled, often this is accomplished only with multiple steps and at considerable expense. Specific instances of quickly reformable molds have been found that rely on beads, sand or other particulate materials being blown or poured into a container with at least one flexible or elastically extensible surface. An article is pushed against or surrounded by the flexible surface and the contained particulate material, and then a vacuum is pulled on the container to remove air so that ambient air pressure consolidates the beads or particles and holds the flexible surface against them in the shape of the article. Likewise, numerous instances have been found of cushions, pads or seats that rely on introducing or vacuuming air from a bead-filled, flexible or stretchable sealed envelope, while other instances have been found of reformable shapes comprising flexible envelopes that contain mixtures of beads or microspheres combined with binding yet flowable lubricants or highly viscous materials. Some of these shapes have been made temperature responsive, so that heat would soften them and cooling would harden them.
The following U.S. patents relate to casting, molding, and fabrication:
U.S. Pat. No. 2,517,902 (Luebkeman);
U.S. Pat. No. 3,962,395 (Hxc3xa4gglund);
U.S. Pat. No. 4,931,241 (Freitag);
U.S. Pat. No. 5,198,167 (Ohta et al.);
U.S. Pat. No. 5,262,121 (Goodno);
U.S. Pat. No. 5,348,070 (Fischer et al.);
U.S. Pat. No. 5,374,388 (Frailey);
U.S. Pat. No. 5,928,597 (Van Ert et al.);
U.S. Pat. No. 5,957,189 (Uzaki et al.);
U.S. Pat. No. 5,971,742 (McCollum); and
U.S. Pat. No. 6,224,808 (Essinger et al.).
The following U.S. patents relate to formable objects of use:
U.S. Pat. No. 3,608,961 (Von Heck);
U.S. Pat. No. 4,327,046 (Davis et al.);
U.S. Pat. No. 4,885,811 (Hayes);
U.S. Pat. No. 4,952,190 (Tarnoff et al.);
U.S. Pat. No. 5,093,138 (Drew et al.);
U.S. Pat. No. 5,556,169 (Parrish et al.);
U.S. Pat. No. 5,881,409 (Pearce); and
U.S. Pat. No. 5,966,763 (Thomas et al.).
In brief, the present invention provides a reversible state-changeable mixture comprising a plurality of solid bodies and a carrier medium, with the carrier medium filling any voids or interstices between the bodies. Within the mixture, the solid bodies can be caused to transition from a formable state, preferably a near-liquid or fluent condition of mobility, to a stable, force-resisting condition through introduction and then extraction of a slight excess quantity of the carrier medium beyond that required to fill the interstices of the bodies when closely packed. In most embodiments, the carrier medium is a liquid preferably excluding any air or other gases from the mixture, and most of the discussion will revolve around such embodiments. However, some embodiments use a carrier medium that is a liquid-gas froth.
The mixture can be rapidly shifted from a formable (preferably near-liquid or fluent) state to a stable force-resisting state and back again to the formable state, through slightly altering the carrier-solid proportions of the mixture, and the invention further provides methods and apparatus for using the mixture. Embodiments are characterized by one or more of the following advantages: the ability to pressurize a mixture and drive it against a complex surface as if it were a liquid; the ability to create a xe2x80x9cnear-netxe2x80x9d or extremely accurate representation of a shape due to the negligible volumetric change that accompanies a state change; the ability to effect the state-change with a very small volume of single-constituent transfer and with consequently small actuation devices without the need for a vacuum pump, without chemical reactions, and with no need for thermal or electrical energy to be applied to the mixture; the ability to greatly alter the volume of any elastic or otherwise dimensionally changeable container, envelope or chamber through the free-flowing transfer of the mixture from one container to another; and the ability to tailor the mixture to satisfy a wide variety of physical specifications in either the flowable or the stable state.
The mixture can be used in reformable molds or other shaping tools, and in reusable templates that capture the dimensions of impressed shapes for transfer to a mold. The mixture can also be used in any product or shape that benefits from the incorporation of arbitrary reformability or precise reconfigurability. The mixtures further provide useful properties for use in a wide range of shock-absorbing, leveling, protective and supportive elements or apparatus.
The mixture in its formable state may be loosely compared to quicksand, while the mixture in its stable state may resemble hard-packed sand or even cement, with the transition being caused by the transfer of a relatively small amount of liquid. Hence the mixture, while in the formable state, includes enough liquid to fill the interstices between the nested solid bodies, and an excess amount of liquid that is referred to as the transition liquid. In the stable state the transition liquid is absent and the bodies are completely packed or nested.
In preferred embodiments the solid bodies are uniform, generally ordered, and closely spaced, with the predominate mass of the bodies close-packed and touching. To create mobility, the transition liquid is introduced in just-sufficient quantity to create a fluent condition by providing a clearance between some of the bodies, which clearance permits the introduction of at least two simultaneous slip planes between ordered masses of the bodies at any point in the mixture. The bodies themselves separate freely from one another under movement of the liquid and without turbulent mixing, and shift relative to one another generally in ordered bulk masses. The bodies should be of a density that is close enough to that of the liquid to permit flow of the bodies along with the liquid, or should have a size or structure that facilitates movement of the bodies along with the liquid.
In a method according to an embodiment of the invention, the surface of the mixture while in the formable state is first made to conform to a desired shape. The bodies in the mixture are then caused to transition from the fluent condition to the stable condition through extraction of the transition liquid. This extraction removes the clearances required to provide slip-planes between ordered masses of the solid bodies, thereby causing the bodies to make nested, packed, interlocking or otherwise stable consolidated contact. The mixture, now in the stable state, has a surface that conforms to the desired shape.
The invention provides methods for using the mixture in molds, templates or other products through holding the mixture in, or transferring quantities of the mixture while in the fluent condition into and out of variable-contour or variable-volume containers or chambers. The mixture can be stabilized by removal of the transition liquid, which may cause an elastic membrane to be pushed against the consolidated bodies by ambient pressure, or by transition liquid removal that causes the solid bodies to pack together under liquid tensile forces, thereby creating an ordered, deformation-resisting structure through surface friction or through surface adhesion of one body to another.
Certain preferred embodiments of the invention provide for holding the mixture inside a container or transporting the mixture into a container with at least one flexible, elastically deformable and stretchable wall, and then extracting the transition liquid from the mixture so as to cause body-to-body contact and force-resisting stability through pressure external to the container acting on the confined, ordered, abutting bodies. Transfer of fluent mixture into and out of the containers, or displacement of mixture within the containers can be accomplished by pressure forces within the mixture, with these forces being distributed uniformly throughout the mixture by the liquid carrier medium.
This distribution of uniform pressure against the surface of each body, coupled with the clearance volume furnished by the transition liquid, assures that the bodies are not forced against one another while the mixture is in the fluent condition. This elimination of body-to-body compression forces in turn prevents the bodies from sticking together and resisting displacement while the mixture is in the fluent condition. Pressure forces in the liquid can be exerted through pressing a shape against an elastic, stretchable membrane that constitutes at least one surface of a chamber substantially filled with the fluent mixture, or such forces within the liquid medium of the fluent mixture may be induced by a two-way pump or other transfer system.
The bodies themselves may have various geometries and may be provided within a state-change mixture in one uniform type, or there may be two or more types or sizes of bodies dispersed or layered within a mixture. For example spherical bodies of one size might have smaller bodies filling the interstices between the larger bodies, or a layer of short fiber bodies might float above a layer of spherical bodies. Flake-like bodies can be also be used, in which case the flat faces of the bodies can be pressed against one another to create a force-resisting body mass. The flat faces provide many times the contact area of abutting spheres, with accordingly higher friction or adhesion potential when consolidated against one another. If the flakes are in the form of a laminate that has one side heavier than the carrier medium and one side lighter, and if the flakes are closely spaced and in a medium which suppresses turbulence and solid body tumbling, the bodies will tend to be supported in, and to be consolidated in, an ordered parallel configuration. In this case, as with the spherical bodies, the transition liquid quantity will be just sufficient to create shear motion of body masses under low displacement forces.
Mixtures with more than one type or size of body can be used with the bodies either intermingled or layered separately, as by differing densities or the inability of bodies of one layer to pass through bodies in the adjacent layer. Bodies of different sizes or types may also be separated from one another by flexible or extensible porous materials or fabrications that allow passage of liquids but not of the confined bodies.
The degree of accuracy or irregularity on the surface of a stabilized mass of the mixture is dependent upon the relationship between the fineness of the bodies and the dimensions to be captured, a covering membrane""s thickness and conformability, and the size and degree of regular packing order of a state-change mixture""s solid bodies. If the bodies are very small compared to the contours of a shape that is to be replicated, or if the interstices between larger bodies in the mixture are filled by such smaller bodies, the mobile solid bodies of the mixture will consolidate and assume a near-net shape relative to any impressed shape when the transition liquid is extracted from the mixture.
In additional embodiments, the mixtures are stored external to one or more molds, tools or fixtures, and are selectively introduced, stabilized and made fluent again in the tools. Formulas of the mixtures or solid bodies and liquids of the mixtures may be stored separately, and may be mixed or separated as required for effective operation of separate elements of a forming or tooling system.
In yet other embodiments, flexible elements containing state-change mixtures are used to capture exterior or interior contours of a shape and to transfer the contours to other state-change elements. Through such xe2x80x9ctemplatingxe2x80x9d operations a negative of a shape or surface may be produced and then a shape or surface identical to the first may be produced by forming the surface of a mixture against the transfer template. Individual elements might also be used to transfer portions of one shape to another shape and so create variations that combine the contours of two or more shapes into a single shape.
In still other embodiments, several elastic, extensible elements filled with state-change mixtures slide freely upon one another and relative to the contained mixtures in order to conform to highly contoured shapes. These embodiments would be used when the elastic stretch of a single membrane element is not sufficient to capture details of a shape.
Further embodiments include methods of displacing fluent mixtures within variable-volume flat elastic envelopes by pressing the envelopes against shapes with exterior air or liquid pressures, or pressing with physical elements such as bundles of rods or fingers that slide relative to one another. The pressing force pressurizes the liquid carrier medium and causes the envelopes to extend and conform to the shapes as the contained fluent mixtures flow within the envelopes under the uniformly distributed pressure forces within the liquid. Embodiments also contemplate the creation of hollow voids within a mixture-containing envelope, with the impressed shape causing the collapse of the voids so that the mixture need not be pumped into and out of a chamber to permit capture of a shape.
Yet other embodiments include methods for creating a sculptable condition in specific state-change mixtures through placing the mixtures in a quasi-stable state. The solid bodies are held in contact by extraction of a portion of the transition liquid, yet have sufficient lubricity or low contact friction to be displaced relative to one another by externally imposed forces. The bodies can be displaced into voids created within a mass of the quasi-consolidated mixture, or can be progressively displaced along the surface of the mixture from one region of the mass to another. In some embodiments, properties of flow of the mixture and the resistance to deformation of the abutted bodies are predetermined so as to be a function of the imposed external forces, and so to be subject to variable control that allows intermediate quasi-stable, sculptable or displaceable conditions within or on the surface of the bulk mixture.
State-change mixtures may also use solid bodies along with a state-changeable liquid carrier medium. The method for changing the mixture from fluent to stable and back again is, as described above, through transfer of a small amount of excess liquid; however, the mixture can be further solidified by changing the state of the carrier medium from liquid to solid.
In yet another embodiment, a state-change mixture is consolidated within a mold chamber and the liquid carrier or a second liquid component is circulated while held to a pressure below ambient. Through heating and cooling of the circulating liquid, the mold itself can be heated or cooled.
Still another embodiment of the state-change mixture has solid bodies that are hollow and very light, and a carrier medium comprising a liquid-gas froth of similar density. The froth is destroyed when extracted since the gas within it expands and separates from the liquid component; then the froth is reconstituted from the liquid and gas and reintroduced into the body mass to recreate a fluent mixture. The liquid component of the froth may be a solvatable (solvent-releasable) adhesive that can dried to hold the consolidated bodies together and then re-dissolved by the frothed carrier medium. Very light bodies can also surrounded by a denser liquid, with the mixture likewise becoming fluent and then stabilized with transfer of a small quantity of transition liquid; however, the tendency of the bodies to adhere together under contact pressure is preferably countered, or liquid-like transfer of the mixture, especially through small lines or passages, becomes difficult if not impossible.
In additional flat envelope embodiments internal and external elements improve their functioning as lightweight tooling and templates. Included are methods to support these mixture-containing envelope structures, both internally with flexible reinforcements and externally with tubular xe2x80x98footxe2x80x99 structures that also contain state-change mixtures. The flat envelopes may also be backed or supported by liquids or dry media as extensively shown in prior art; e.g., U.S. Pat. No. 5,971,742 to McCollum, U.S. Pat. No. 5,374,388 to Frailey, U.S. Pat. No. 3,962,395 to Hxc3xa4gglund, and others. However, the novel properties of the current invention improve significantly on the art by combining the ability to capture precise impressions of a shape with the ability to be switched from a liquid-like state to a firm state, or even to a fully hardened state that resembles concrete yet can be returned to a formable condition.
Finally a diagram of a prototype tool-forming system is shown, and operations are described in which shapes are impressed by pattern parts against a single membrane backed by the state-change mixture; the mixture is consolidated by transition liquid removal; and the mixture is then hardened into a porous tool by the extraction of water vapor from the residual liquid, thereby activating a water-soluble adhesive. The prototype system is self-contained on a rolling cart and the tool can be separated from the system for use in various materials forming processes.
To reiterate, according to embodiments of the invention, the state change from liquid-like to solid-like properties within the mixtures is effected by the transfer of a small amount of excess carrier medium, the transition liquid, into and out of the mixtures. When the transition liquid is present, preferably in just-sufficient quantity to create the degree of support and clearance that provides for at least two slip-planes, the solid bodies have a degree of mobility similar to that of the liquid medium of the mixture. The slip-plane condition of mobility can be generated through very small liquid pressure differentials or through externally imposed forces that displace the carrier liquid and the supported bodies along with the liquid. Ordered bulk masses of the bodies can shift relative to other ordered masses at any point within a continuous volume of the mixture, and the location of the slip-planes can fluidly shift under any slight differential force transferred from one body to another. It is preferred to prevent frictional contact between bodies during such force transfer by having the liquid medium of the mixture furnish a viscous or xe2x80x98streamingxe2x80x99 resistance to contact, and also for the medium to furnish a degree of body-surface lubrication so that light body contacts do not create friction between bodies.
Lubricity under high contact forces, as is required for many lubricating media, is not necessary within the mixtures since the bodies are in effect free-floating during flow, with any imposed liquid pressure forces being uniformly distributed against the surface of each body. For example a nearly ideal aqueous liquid medium can be formed by dissolving a small quantity of a soluble long-chain polymer such as polyethylene oxide into water. The medium carries solid bodies of a similar density without turbulence and friction-producing contact, allows the bodies to make non-lubricated surface contact when the medium is extracted, and causes the bodies to readily separate when the transition liquid is reintroduced.
When the transition liquid is extracted so that the solid bodies are in a stable configuration with ordered, packed and consolidated contact, the degree of resistance to externally imposed forces depends on such tailorable, engineered physical properties as body shape, body elasticity and compressibility, body surface properties of roughness, smoothness or natural molecular adhesion, residual adhesiveness or lubricity of the liquid medium on the contacting surfaces, surface tension of the medium, and variations of liquid medium or body properties with changes of temperature or pressure; alteration of the resistance properties through replacement of the first liquid with a second liquid medium, rinsing of the bodies and the first medium with a second or sequential liquid media, vapors or gaseous fluids; and any other engineered variations in the bodies and first liquid medium, and in other sequential introductions of various fluids into the mixtures or through the consolidated bodies. Any adhesive or clinging contact between the bodies is preferably relieved through polar molecular action of the first liquid medium, or through an intermediary treatment with other liquids or fluids prior to reintroduction of the first liquid medium.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.